Belgians are primarily a nationality or citizen group, by jus soli (Latin: right of the soil),[14] also known as birthright citizenship, and are not a homogeneous ethnic group.[15][16][17] Belgians are made up of two main linguistic and ethnic groups; the Dutch-speakers (called the Flemish) and the French-speakers (mostly Walloons), as well as a third tiny but constitutionally recognized group from two small German-speaking areas. These sometimes competing ethnic and linguistic priorities are governed by constitutionally designated "regions or communities", depending on the constitutional realm of the topic, a complex and uniquely Belgian political construct. Since many Belgians are at least bilingual, or even trilingual, it is common for business, social and family networks to include members of the various ethnic groups composing Belgium.[citation needed]

The Brussels-Capital Region occupies a unique political and cultural position since geographically and linguistically it is a bilingual enclave within the unilingual Flemish Region. Since the founding of the Kingdom of Belgium in 1830, the city of Brussels has transformed from being almost entirely Dutch-speaking into a multilingual city with French as the majority language and lingua franca, a process that has been labelled the Frenchification of Brussels".[18]

Within Belgium the Flemish, about 60% of the population, form a clearly distinguishable group, set apart by their language and customs. However, when compared to the Netherlands most of these cultural and linguistic boundaries quickly fade, as the Flemish share the same language, similar or identical customs and (though only with the southern part of today's Netherlands) traditional religion with the Dutch.[21]

However, the popular perception of being a single polity varies greatly, depending on subject matter, locality and personal background. Generally, Flemings will seldom identify themselves as being Dutch and vice versa, especially on a national level.[22]

Walloons are a French-speaking people who live in Belgium, principally in Wallonia. Walloons are a distinctive community within Belgium,[23] important historical and anthropological criteria (religion, language, traditions, folklore) bind Walloons to the French people.[24][25] More generally, the term also refers to the inhabitants of the Walloon Region. They may speak regional languages such as Walloon (with Picard in the West and Lorrain in the South).

Though roughly three-quarters of Belgium's French speakers live in Wallonia, it is important to note that French-speaking residents of Brussels tend not to identify as Walloons.

The German-speaking Community of Belgium is one of the three constitutionally recognized federal communities of Belgium.[26] Covering an area of less than 1,000 km2 within the province of Liège in Wallonia, it includes nine of the eleven municipalities of the so-called East Cantons and the local population numbers over 73,000 — less than 1% of the national total. Bordering the Netherlands, Germany and Luxembourg, the area has its own parliament and government at Eupen.

The German-speaking community is composed of the German-speaking parts of the lands that were annexed in 1920 from Germany. In addition, in contemporary Belgium there are also some other German-speaking areas that belonged to Belgium even before 1920, but they are not currently considered officially part of the German-speaking community in Belgium: Bleiberg-Welkenraat-Baelen in Northeastern province of Liège and Arelerland (city of Arlon and some of its nearby villages in Southeastern province of Belgian Luxembourg). However, in these localities, the German language is highly endangered due to the adoption of French.[27]

Roman Catholicism has traditionally been Belgium's majority religion with approximately 65% of the Belgians declaring themselves to be Catholics.[28] However, by 2004, nationwide Sunday church attendance was only about 4 to 8% (9% for Flanders only). A 2006 inquiry in Flanders, long considered more religious than the Brussels or Wallonia regions in Belgium, showed 55% of its inhabitants calling themselves religious while 36% said that they believed that God created the world.[29]

Belgium had a population of 10,839,905 people on 1 January 2010, an increase of 601,000 in comparison to 2000 (10,239,085 inhabitants). Between 1990 (9,947,782 inhabitants) and 2000 the increase was only 291,000. The population of Flanders, Wallonia and Brussels on 1 January 2010 was 6,251,983 (57.7%), 3,498,384 (32.3%) and 1,089,538 (10.1%), respectively.

^Footnote: The Celtic and/or Germanic influences on and origin(s) of the Belgae remains disputed. Further reading e.g. Witt, Constanze Maria (May 1997). "Ethnic and Cultural Identity". Barbarians on the Greek Periphery?—Origins of Celtic Art. Institute for Advanced Technology in the Humanities, University of Virginia. Archived from the original on 10 June 2007. Retrieved 6 June 2007.

^Ethnic Groups Worldwide, a ready reference Handbook, David Levinson, ORYX Press, (ISBN 1-57356-019-7), p. 13 : « Walloons are identified through their residence in Wallonia and by speaking dialects of French. They, too, are descended from the original Celtic inhabitants of the region and Romans and Franks who arrived later. Walloons are mainly Roman catholic. »

^The Encyclopedia of the Peoples of the World, A Henri Holt Reference Book, page 645 : « Culturally there is continuity between the French and the Walloons, Wallon culture consisting mainly of dialect literary productions. While historically most Wallons came within France's cultural orbit

^"Discrimination in the EU in 2012"(PDF), Special Eurobarometer, 383, European Union: European Commission, p. 233, 2012, retrieved 14 August 2013 The question asked was "Do you consider yourself to be...?" With a card showing: Catholic, Orthodox, Protestant, Other Christian, Jewish, Muslim, Sikh, Buddhist, Hindu, Atheist, and Non-believer/Agnostic. Space was given for Other (SPONTANEOUS) and DK. Jewish, Sikh, Buddhist, Hindu did not reach the 1% threshold.

^Inquiry by 'Vepec', 'Vereniging voor Promotie en Communicatie' (Organisation for Promotion and Communication), published in Knack magazine 22 November 2006 p.14 (The Dutch language term 'gelovig' was translated in the text as 'religious', more precisely it is a very common word for believing in particular in any kind of god in a monotheistic sense, and/or in some afterlife.